Battery charge determination

Abstract

A method of determining a current state of charge of a battery having an internal resistance includes estimating the current state of charge of the battery at a current time as a function of a previous state of charge of the battery at a previous time, a battery voltage of the battery during a time interval between the previous time and the current time, and a value of the internal resistance of the battery. The method improves the determining of the current state of charge of a battery.

What is claimed is: 
     
       1. A method for determining a current state of charge of a battery having an internal resistance, comprising:
 during a charge or discharge phase, iteratively estimating, in a CPU, the current state of charge (SOC new ) of the battery at a current time as a function of a previous state of charge (SOC old ) of the battery at a previous time, a battery voltage (V t ) of the battery during a time interval (t) between the previous time and the current time, and a value (R i ) of the internal resistance of the battery wherein at each iteration, the most recently estimated SOC new  is used as the SOC old  for the next estimation; and 
 during an idle phase, stopping the iterative estimation and determining a current idle state of charge SOC idle     —     new ) of the battery as a value associated to a current voltage value (V idle ) of the battery using a predetermined relation between an open-circuit voltage (OCV) and a state of charge (SOC) of the battery. 
 
     
     
       2. The method of  claim 1 , wherein estimating the current state of charge (SOC new ) comprises estimating a charge provided by or to the battery during the time interval (t) as a function of the battery voltage (V t ) and the value (R i ) of the internal resistance. 
     
     
       3. The method of  claim 2 , wherein estimating the charge provided by or to the battery during the time interval (t) comprises determining a value representative of the difference (V diff ) between the battery voltage (V t ) and an open-circuit voltage value (OCV t ) of the battery during the time interval (t). 
     
     
       4. The method of  claim 3 , wherein determining the value representative of the difference (V diff ) comprises determining the open-circuit voltage (OCV t ) of the battery during the time interval (t) as a value associated to the previous state of charge (SOC old ) in a predetermined relation between the open-circuit voltage (OCV) and the state of charge (SOC) of the battery. 
     
     
       5. The method of  claim 1 , wherein estimating the current state of charge (SOC new ) comprises
 making a plurality of measures of the voltage of the battery over the time interval (t); and 
 determining the battery voltage (V t ) of the battery during the time interval (t) as an average of the plurality of measures. 
 
     
     
       6. The method of  claim 1 , further comprising detecting the idle state of the battery by detecting that an electric current provided by or to the battery has dropped below a predefined threshold. 
     
     
       7. The method of  claim 1 , further comprising determining an improved internal resistance value as a function of: the current idle state of charge (SOC idle     —     new ), and a previous idle state of charge (SOC idle     —     old ) of the battery at a beginning of the charge phase or the discharge phase. 
     
     
       8. The method of  claim 7 , wherein determining the improved internal resistance value comprises determining an average electric current (I Avg ) provided by or to the battery during the charge phase or the discharge phase by comparing the current idle state of charge (SOC idle     —     new ) to the previous idle state of charge (SOC idle     —     old ), and dividing a value representative of the difference between the battery voltage (V) and the open-circuit voltage (OCV) during the charge phase or the discharge phase by the average electric current (I Avg ). 
     
     
       9. The method of  claim 7 , wherein the internal resistance value (R i ) used for estimating the state of charge during a next charge phase or a next discharge phase is the improved resistance value or an average of values including the improved internal resistance value and at least one previously used resistance value. 
     
     
       10. A non-transitory computer readable medium having recorded thereon program steps operative to cause a CPU to determine a current state of charge of a battery having an internal resistance by performing the steps of
 during a charge or discharge phase, iteratively estimating the current state of charge (SOC new ) of the battery at a current time as a function of a previous state of charge (SOC old ) of the battery at a previous time, a battery voltage (V i ) of the battery during a time interval (t) between the previous time and the current time, and a value (R i ) of the internal resistance of the battery wherein at each iteration, the most recently estimated SOC new  is used as the SOC old  for the next estimation; and 
 during an idle phase, stopping the iterative estimation and determining a current idle state of charge (SOC idle     —     new ) of the battery as a value associated to a current voltage value (V idle ) of the battery using a predetermined relation between an open-circuit voltage (OCV) and a state of charge (SOC) of the battery. 
 
     
     
       11. An electronic device, comprising:
 a battery having an internal resistance; 
 memory; and 
 a CPU operatively connected to the memory, the CPU operative to,
 during a charge or discharge phase, iteratively estimating the current state of charge (SOC new ) of the battery at a current time as a function of a previous state of charge (SOC old ) of the battery at a previous time, a battery voltage (V t ) of the battery during a time interval (t) between the previous time and the current time, and a value (R i ) of the internal resistance of the battery wherein at each iteration, the most recently estimated SOC new  is used as the SOC old  for the next estimation; and 
 during an idle phase, stopping the iterative estimation and determining a current idle state of charge SOC idle     —     new ) of the battery as a value associated to a current voltage value (V idle ) of the battery using a predetermined relation between an open-circuit voltage (OCV) and a state of charge (SOC) of the battery. 
 
 
     
     
       12. The device of  claim 11 , wherein the device is a mobile communication device, and further comprising:
 a transceiver operative to effect wireless communications with a wireless communication network.